This invention relates to pulse detonation systems, and more particularly, to two-stage pulse detonation systems.
Variable cycle turbofan ramjet engines may be used to provide aircraft flight speeds between low subsonic Mach numbers to high supersonic Mach numbers of about Mach 6. Known engines include a core engine system and a dual mode augmentor. The dual mode augmentor provides additional heat to exhaust airflow exiting the core engine system to increase engine thrust. The core engine system provides power to drive a fan assembly and typically includes in serial, axial flow relationship, a compressor, a combustor, a high pressure turbine, and a low pressure turbine. The dual mode augmentor is positioned downstream from the core engine and receives air from the core engine and a bypass duct surrounding the core engine.
Known engines can operate over a wide range of flight speed operations if several different combustion systems are utilized. During flight speed operations from take-off to approximately Mach 3, the core engine and an engine fan system provide airflow at a pressure and quantity used by the augmentor to produce thrust for the engine. To maintain flight speed operations between Mach 3 and Mach 6, the core engine system is shut-down and ram air flow is introduced into the dual mode augmentor either by windmilling the fan system or by utilizing an auxiliary ram duct. To sustain flight speed operations above Mach 6, either a separate supersonic combustion system, i.e., a scramjet, is used, or a separate rocket-based thrust producing system is used. To achieve flight speed operations in space, the rocketbased thrust producing system is used. As a result, for an engine to operate efficiently over a wide range of operating flight speeds, several different combustion systems are used.
Efforts to address the drawback of needing a combination of combustion systems to obtain a wide range of flight speeds have led to the development of pulse detonation engines, which aid in increasing the available flight speed range while reducing the need for a combination of combustion systems.
One implementation that has been proposed for an engine with a pulse detonation system contains at least one tube pulse detonation engine (PDE). The PDE can be positioned as an augmentor or as the main combustor or both. However, tube pulse detonation systems have some drawbacks. These systems use mechanical valves to aid in the control of the detonation, which add complexity and cost, as well as a limit to the detonation frequency that can be achieved. Lower detonation frequencies can also adversely affect the components within the engine system because of the shock and vibrations created by the detonations. Furthermore, tube PDE systems do not operate efficiently with commonly used aviation fuels. The 2-stage PDE that is described in this invention fills the need of using aviation fuels and high frequency operation. Thrust is generated using detonations which is proven to be the most efficient way to extract energy from a given fuel-air mixture which is detonable.